81977988 has 12 divisors (see below), whose sum is σ = 191282000. Its totient is φ = 27325992.

The previous prime is 81977947. The next prime is 81978007. The reversal of 81977988 is 88977918.

It is a tau number, because it is divible by the number of its divisors (12).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3415738 + ... + 3415761.

Almost surely, 2^81977988 is an apocalyptic number.

It is an amenable number.

81977988 is an abundant number, since it is smaller than the sum of its proper divisors (109304012).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81977988 is a wasteful number, since it uses less digits than its factorization.

81977988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6831506 (or 6831504 counting only the distinct ones).

The product of its digits is 2032128, while the sum is 57.

The square root of 81977988 is about 9054.1696471847. The cubic root of 81977988 is about 434.4092708188.

The spelling of 81977988 in words is "eighty-one million, nine hundred seventy-seven thousand, nine hundred eighty-eight".